The invention relates to spring probe assemblies.
This invention relates to spring probe assemblies which will mate to some type of planar device, like a printed circuit board (PCB). The spring probe assemblies use spring-loaded pins, of appropriate spring force, to transfer the signal from a signal source to the circuitry of the planar device. This process is normally accomplished using spring probes assemblies, which have well matched impedances, whose ground shields are linked together in a metal block. Ground spring probes located in various locations in the metal block then form the signal return path.
It is known that some planar devices require the interface of signals of various frequencies. In such cases the use of common grounds, as the signal return path for those various frequencies, will result in what is called common mode problems which degrade the quality of the signals being sent to and from the planar device.
It is therefore an object of the invention to improve the quality of the signals transmitted through a spring probe assembly.
It is furthermore an object of the invention to eliminate common mode problems in spring probe assemblies in which signals of differing frequencies are present.
It is furthermore an object of the invention to facilitate repair of spring probe assemblies.
These and other objects of the invention are achieved by providing a spring probe assembly with an insulating housing having a plurality of openings in a front face of the insulating housing. Each of the openings has a first part and a second part which are connected together by a channel in the insulating housing. One or more first probes are disposed in the first parts of the openings and one or more second probes disposed in the second parts of the openings. Clips are disposed in the channels and these connect electrically the one or more first probes to the one or more second probes.
The use of an insulating housing with two different probes allows one of the probes to carry signals and the other one of the probes to be connected separately to ground. Each of the two different probes can be isolated from one another, and thus signal integrity is improved. It is possible to connect two or more of one type of the probes to a single one of the other type of probes. Furthermore, each of the probes can be separately replaced, which improves the reparability of the assembly. The relationship of the pairs of the probes is chosen such that there is minimum interference due to common mode and maximum transference of the intended high speed signal with a minimum of signal degradation.
A further advantage of the invention is that two or more different ones of the first probes can each carry signals of different frequencies. Each of the two or more different ones of the first probes are isolated from each other, and there is therefore little or no interaction between each of the probes, and cross-talk between signals is minimized.
In one embodiment of the invention, the first parts of the plurality of openings extend through the insulating housing from the front face to a back face and thus allows easy connection of the probe in the first parts of the openings to be connected to a coaxial cable.
The first probes are constructed such that they have a central probe conductor placed within an outer probe receptacle and an outer probe shield disposed about the first outer probe receptacle. The outer probe shield is electrically insulated from the central probe conductor. In this construction, the first probes can carry a signal which is shielded from interference by the outer probe shield. The outer probe shield is connected to the shield of the coaxial cable, and the central probe conductor is connected to the central cable conductor of the coaxial cable.
The second probes have a second central probe conductor and a second outer probe receptacle disposed in second parts of the plurality of the openings. The clips connect the first probe shield of the first probes with the second outer probe receptacle. In this configuration, the second probes carry the grounds. The first probe shields are isolated from each other, thus improving signal integrity over prior art constructions. One or more of the second probes are connected to a single first probe shield by means of one or more clips.